Analyzing the data on 2010 from National Vulnerability Database reveals some interesting statistics.

This is the list of the top most targeted applications in 2010:

As more and more businesses and applications are moving to the web, browsers are the favorite targets for hackers and security researchers. These are followed closely by Adobe tools, Microsoft Office, RealPlayer and Java Runtime Environment.

The top most targeted operating systems in 2010 are the following:

Microsoft still remains the preferred target when talking about operating systems, followed very far behind by Linux, Apple Mac OS X and Cisco IOS.

From the data above we can see that 75% of vulnerabilities are targeting applications, 18% operating systems and 7% hardware devices (i.e. Cisco). This means that patching only Microsoft products is not enough. Adobe products, web browsers and Java Runtime Environment are the minimum set of other applications that must be monitored closely to ensure they are always fully patched for adequate security.